The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Engines such as diesel engines and compression ignition engines may produce particulate matter (PM) that is filtered from exhaust gas and collected by a PM filter. The PM filter is disposed in an exhaust system of the engine. The PM filter reduces emissions of PM generated during combustion. Over time, the PM filter becomes full. During a process called regeneration, the PM may be burned within the PM filter.
There are various ways to perform regeneration including modifying engine management, using a fuel burner, using a catalytic oxidizer to increase the exhaust temperature with after injection of fuel, using resistive heating coils, and/or using microwave energy. The resistive heating coils are typically arranged in contact with the PM filter to allow heating by both conduction and convection.
An engine control module (ECM) may regenerate the PM filter using an electrical heating technique. The electrical heating technique refers to the electrical heating of the exhaust gas entering the PM filter. One or more electrical coils may be disposed upstream from the PM filter and may be activated to heat the exhaust gas. The heated exhaust gas ignites PM in the PM filter which combusts through channels in the PM filter. Exhaust gas flow advances the PM through the channels.
The electrical heating technique provides a quick heating and light-off of the PM. Electrically heated PM reduction systems reduce fuel economy by a negligible amount but may be operation-limited based on exhaust flow. As exhaust gas flow increases, for example, above a particular flow rate (kg/s), the ability to initiate regeneration by the electrically heated element decreases. Furthermore, the ability to maintain PM combustion through the channels decreases when the exhaust gas flow increases above a particular flow rate.
The ECM may also control combustion in the engine to improve fuel economy of a vehicle and/or reduce emissions. During periods when the engine would normally be idling, such as when a driver applies a brake input and the vehicle is stopped, the ECM may stop fueling to the engine to stop combustion. When the engine stops, exhaust gas stops flowing through the exhaust system. When the ECM determines the driver is about to accelerate the vehicle, such as by releasing the brake input, the ECM may start the engine using an electric motor such as an engine starter. Combustion starts and exhaust gas begins to flow through the exhaust system.